In a typical light-imaging sensor system, a feature in a scene is imaged onto an image surface by optical elements such as lenses and mirrors. A detector segmented array formed of a number of detector subelements is located at the image surface, so that the feature is imaged onto the detector array. The output signals of the detector subelements are amplified and supplied to an image-processing computer, which determines the location and nature of the image of the feature.
The detector array may be a one-dimensional or linear array of detector subelements that is optionally scanned over the scene to produce a two-dimensional image. The detector array may instead be a two-dimensional areal or staring array of detector subelements. The one-dimensional array has the advantage of a smaller number of detector subelements and processing channels, and consequently a lower cost, as compared with the two-dimensional staring array. It also has a cost advantage for multispectral sensing, in which parallel arrays of ordinary detectors are used with spectral filters or spectral dispersive elements, whereas staring detectors require extraordinary construction for just two-color or three-color sensing. On the other hand, the one-dimensional array requires a scanning mechanism for many applications, although in other applications the scanning movement may be produced by the motion of the platform that carries the imaging sensor system.
The accuracy of the determination of the location of the feature is a crucial concern in such imaging sensors. The spatial location of the image on the detector array may be translated geometrically into an angle of the feature relative to a reference axis of the sensor, such as the boresight of the platform that carries the sensor.
In the usual approach, the spatial location of the feature is determined by observing which detector subelement intercepts the image of the feature. However, in both the one-dimensional and two-dimensional detector arrays, there is a natural locational uncertainty of the image within the detector subelement. If the detector subelements are made smaller to reduce this uncertainly, “edge effects” between adjacent detector subelements introduce a locational uncertainty, as the image of the feature may not fall entirely within a single detector subelement, as well as a loss of sensitivity because the signal energy of the feature is split between two or more detector subelements. The accuracy of the location determination is thus limited by the geometry and absolute size of the detector subelements.
There is a need for an improved approach for the structure of the detector array and the analysis of the output signals of the detectors to achieve increased accuracy in the determination of the location of the image of the feature. The present invention fulfills this need, and further provides related advantages.